Partially Filled Pipe Ultrasonic Flow meter

Partially filled pipe Ultrasonic flowmeter is designed for partially filled pipe applications, It has the same measurement as the doppler ultrasonic flowmeter of full filled pipe in the fluid velocity measurement.

Principle

When measuring liquid velocity, the flow meter operates by transmitting an ultrasonic sound from its transmitting transducer, the sound will be reflected by useful sonic reflectors suspended within the liquid and recorded by the receiving transducer. If the sonic reflectors are moving within the sound transmission path, sound waves will be reflected at a frequency shifted (Doppler frequency) from the transmitted frequency. The shift in frequency will be directly related to the speed of the moving particle or bubble. This shift in frequency is interpreted by the instrument and converted to various user defined measuring units.

We have two method to measure the liquid level, one uses the ultrasonic level meter of special small-scale and low dead zone to measure the level. When installing the level meter, user needs to fix a welding base, the height welding base is usually 80～100mm, so it can ensure a high measurement accuracy. The other uses pressure sensor placed on or near the bottom watershed.

The flow formula of partially filled pipe: Q = V·A

Where  

        V    -    Fluid velocity in pipe

        A    -    Cross-sectional area of liquid in pipe

A is the function of liquid level and inner diameter, A = f（D·h）

Where  

        D    -    Inner diameter of pipe

        h    -     Liquid level

When the pipe is partially filled with liquid, Cross-sectional area of liquid is calculated as below:

Cross-sectional area of liquid (liquid level is below pipe centerline)